Posts tagged ‘Biology’

Neurotransmission.

Your body is more amazing and complicated than anything on this Earth; everything is tailored to work perfectly in synchronisation with everything else. From the beautiful complexity of the brain, to the admirably simple structure of the heart (in comparison), we are alive because of their cooperation and constant hard work. Most people pass through life unaware of the prodigious, intricate network of systems which constitute our anatomy.

Every system in the human body is specific to a function. From the skeletal system – providing rigidity, protection and structure to the body – to the circulatory system – keeping cells rich in oxygen and other essential nutrients using blood – we could not survive as we are without all fifteen systems*.

The Nervous System is one of those fifteen other systems, and is concerned with the transmission of electrical impulses and information. It is the nervous system that will make you feel that annoying poke from the person next to you, but also will initiate reflexes, such as when you touch a hot pan. In fact, ANY piece of information that needs to get from one place to another will be transferred thanks to the nervous system.

To understand neurotransmission, the anatomy of the neurones in the body must be understood.

The anatomy of a Neurone.

Many of the features of a neurone are irrelevant to this article, but if you’re interested in knowing more, feel free to contact me.

The important parts to note are:

  • The cell body – this contains the DNA for the structure and controls what the cell does.
  • The dendrites – these receive information from other neurones, where they’re processed at the
  • Axon hillock – this decides whether the received information is relevant, and whether an impulse should be sent.
  • Axon – this is the pathway which the electrical impulses (hence information) travel.
  • Terminal buttons – these are the most important for this post. It is here that neurotransmission takes place. They may also be called synaptic knobs, synaptic endings, axon terminals and many other names.

So what is the purpose of the terminal buttons?

Neurones are in every part of your body, so they need to branch off in all directions; it is not feasible to have one giant neurone that travels everywhere. As thousands of impulses are sent every second, this is another reason that we need so many neurones (just to illustrate, we have 20,000 neurones per mm³ in the brain – meaning approximately 10,000,000,000,000 in the brain alone).

This means, that with so many neurones in the body, they will need to transfer signals between each other so they reach their destination successfully. The terminal buttons are an important aspect of this process, known as neurotransmission.

The following video will provide a basic knowledge of the process, I highly advise you watch it before proceeding (it’s only 1 minute 19!).

As you can see, chemicals play a vital role in the transmission of signals. So what is the process?

  1. The impulse (action potential) arrives at the terminal button.
  2. Gated Ca2+ (calcium ion) channels open due to the electrical impulse, causing an influx of the ions.
  3. This influx causes synaptic vesicles to diffuse to the terminal button membrane and release the neurotransmitters inside.
  4. Once in the synaptic cleft, the neurotransmitters diffuse over to receptors on the post-synaptic neurone.
  5. The neurotransmitters then bind with the receptors. Only the correct neurotransmitters can bind to the receptors (much like a lock and key). The action potential is transferred to the post-synaptic neurone.
  6. The neurotransmitter is then destroyed with enzymes and recycled; it is reabsorbed into the pre-synaptic neurone, which is facilitated with uptake pumps. This allows the neurotransmitters to be used again next time.

Types of neurotransmitters: a brief overview.

So what are the most important neurotransmitters, and what do they do?
Neurotransmitters marked with a * have a large importance within Psychology.

Acetylcholine:
This was one of the first neurotransmitters discovered. It’s main purpose is the stimulation or inhibition of movement in skeletal muscle. This neurotransmitter is usually found in the brain and peripheral nervous system. It has also been found to have impact on memory and learning. Other uses include slowing of the heart, contraction of the gut area and stimulation of mucus and saliva production.

Dopamine*:
Dopamine is the pleasure neurotransmitter. Drugs such as cocaine, ecstasy and alcohol stimulate the release of Dopamine, causing a feeling of happiness and stimulation (although alcohol is technically a depressant). In the brain, it actually controls movement, and can help with the regulation of information flow. People with Parkinson’s disease have a lack of Dopamine in the brain interior, causing motor problems. This neurotransmitter is important in Clinical Psychology, as Schizophrenics suffer a lack of Dopamine in the frontal lobe. This clouds their thinking and causes their distinct symptoms.

Noradrenaline (aka Norepinephrine)*:
This is involved in the regulation of mood. In Psychology, this is important as low levels of this can be a contributory factor of depression. Very high levels of this can cause stress and aggression; it is released in response to short-term stress and therefore causes the heart rate and blood pressure to increase. High levels of this, mixed with high levels of dopamine and phenylethalimine have actually been found to cause the infatuation emotion. When you’re feeling wildly in love, blame this mixture of neurotransmitters! Biologically, it increases levels of glycogen conversion in the liver, and conversion of fats to fatty acids. It also relaxes bronchial muscles, allowing easier breathing.

Serotonin*:
This is the prime neurotransmitter regulating mood, sleep, emotion and appetite. A large amount causes inhibition of appetite, small amounts cause cravings for food. Many people mistake Serotonin for Anandamide, which is what causes the food cravings and sleepiness when smoking cannabis. Serotonin in low levels has been linked to depression, and violent/aggressive behaviour.

Those are some of the main neurotransmitters, although there are many many more.

Relevance to Psychology

So why do Psychologists care about neurones and neurotransmission? Well as explained in the neurotransmitter section, lack/excess of some of them can contribute to psychological disorders, such as depression, schizophrenia and insomnia. Psychiatrists often have to prescribe medication to restore the balance between certain levels of neurotransmitters in the brain. Therefore, it is essential that Psychologists have an understanding of the nervous system and the chemical nature of the brain.

Further reading/viewing for the keen.
Favourite links are in bold.

http://science.education.nih.gov/supplements/nih2/Addiction/activities/lesson2_neurotransmission.htm
http://www.mind.ilstu.edu/curriculum/neurons_intro/neurons_intro.php (
HIGHLY recommended! ^^^)
http://www.trap17.com/index.php/neurotransmitters_t59121.html
http://en.wikipedia.org/wiki/Neurotransmitter
http://www.drugabuse.gov/pubs/teaching/Teaching2/largegifs/slide8.gif

Thanks for reading,

Samuel Eddy.

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March 17, 2010 at 4:00 pm 4 comments

The Psychology of Sleep.

Assuming you live to the average life expectancy of approximately 67 years, you will spend a phenomenal 208,000 hours sleeping. That equates to just over 20 years sleeping – an entire 33% of your lifespan. Provided you get your 8 hours of sleep a night on average, you’ll dedicate roughly 80,000 hours of that on dreaming (this, however, is extremely approximate as everybody dreams different amounts and enters REM sleep at different times; this will be explained later). Considering we sacrifice 1/3 of our lives to sleep, there must be a reason for it? This article will explore the following:

  • The 5 stages of sleep, and what happens in each stage.
  • The reasons we have to sleep, and what would (theoretically) happen if we do not.

An article explaining the Psychology of dreams will be available at a later date.

WHAT HAPPENS WHEN WE SLEEP?

Click to view the larger image

The five stages of sleep and their frequencies.

Sleeping, as described in the introduction, forms a massive part of our life. If you look at the above image, you can see the rough cycle that one would progress through when sleeping. The average human will complete three cycles of sleep in one night. Depending on your own body though, this can range from one cycle to four or five. Before I explain what happens in each stage, it is worthwhile explaining how we test for sleep. By testing electrical impulses in the brain, we can determine what stage someone is in during sleep, The five different stages provoke different brainwaves. It is important to understand these brainwaves in order to appreciate what happens in each of the stages. Consider the following diagram:

Click to see the image larger.

Brainwave activity during sleep.

With that diagram here, I can now explain the five stages.

Stage ‘0’ – Drowsiness
Sometimes this stage is not included in diagrams. This stage is when the human is still entirely conscious, but feels the need to sleep. Consider this to be the point where you say to someone “Wow, I’m shattered!” Brainwaves are random, small and fast (these are not shown on the diagram – visit this link for more detailed brainwaves: http://bit.ly/bS2KAV)

Stage 1 –  Very light sleep; practically daydreaming
You could consider this stage as “dozing off”. The eyes begin to roll slightly in the head, and your mind tends to wander a little. Brainwaves at this stage consist mainly of theta waves and occasionally alpha waves (these are present mainly when awake). If your body is ready, and you are free from noise or distraction, you will only be in this stage for a few minutes.

Stage 2 – Light sleep
During this stage, the brainwave activity changes slightly. Peaks of waves become higher and are slightly more random. Occasionally, “K-Complexes” will occur. These are dramatic and sudden bursts of activity, which result in a very high brainwave. If you note the diagram above, a K-Complex occurs towards the far right of the brainwave for stage 2. K-Complexes occur every 1.0 – 1.7 minutes and are often followed by “sleep spindles” which are bursts of many brainwaves (note the dense area of activity on the far left of the stage 2 brainwave). It seems like K-Complexes occur in response to environmental stimuli, such as noise or touching the skin. The burst of activity may be for the brain to work out whether the situation is dangerous or not, and if so it will wake you up. The heart rate slows during this stage, and body temperature drops slightly.

Stage 3 and 4 – Deep sleep and Very Deep Sleep, respectively.
Brainwaves during this are much higher, and less frequent. In stage 3, about 25% of brainwaves are delta waves (the remainder being theta waves). This changes to about 50% delta and 50% theta in stage 4. It is very difficult to wake someone up during this stage of sleep, but if you do, they’ll wake up extremely irritated and moody. Blood flow to the brain decreases, and is focused on muscles – evidence that restoration of other organs and tissue occurs during this stage. The brain is “free” to wander and regain the huge amount of energy used during the day.

Before entering REM sleep (stage 5), the stages reverse. So the person sleeping will go stage 1 – 4, then 4-1 then REM.

Stage 5 – REM sleep; dreams occur here.
During this stage the body is paralysed. This is to prevent you from acting out anything you dream – imagine jumping down stairs in real life just because you are dreaming it! Brainwaves revert to being small and rapid – they consist of many beta waves, which are also present when awake. This is support for the idea vivid dreaming is occurring, as the brain is very active. Rapid eye movement occurs quite a lot, and there are occasional muscular twitches. If someone is woken up during this stage, they are MUCH more likely to remember what they were just dreaming. The first time you enter REM during the night, it will only last for about 15 minutes; as the night progresses you spend longer and longer in REM (up to approximately 90 minutes). After, you drift back through stages 1-4, then 4-1 before returning to REM sleep and dreaming again. Dreams can occur in other stages, but they are less vivid, less emotional and less memorable.

WHY DO WE SLEEP?
There are a number of theories as to why we sleep:

  • We need the time to recuperate and “reload” our deposits of energy.
  • Studies suggest most growth and development occurs during sleep.
  • Sleep is needed to consolidate information learnt during the day. Studies show that without sleep, people tended to forget more information they learnt previously.
  • We need sleep to stay in a good mood. Without it, people become irritable and disorientated.
  • Sleep allows the body to replace red and white blood cells easier.

What happens if we don’t?
It has been found (using rats) that lack of sleep can actually lead to death. However, humans will at first begin to experience slowed speech, slow reactions and bad motor functioning. Emotions will cease to the point the person doesn’t care about much and doesn’t react to emotional stimuli. If the person becomes extremely sleep deprived, they will at first experience “micro-sleep”, where by the brain shuts off for 5-10 seconds then ‘boots back up’ again. This is very dangerous and can result in fainting and sickness. If they reach a severe lack of sleep, they will begin to hallucinate as the brain desperately seeks sleep and tries to enter REM. Eventually the person is likely to pass out before they reach a critical, potentially fatal state.

Thanks for reading, be sure to comment and subscribe!


Sam Eddy.

Sources and good further reading:
My own knowledge and information from lectures.
http://www.psychologistworld.com/sleep/

http://www.dreamviews.com/sleepstages.php
http://www.scottsdalecc.edu/ricker/psy101/readings/section_2/images/EEGSleepStages.jpghttp://www.helpguide.org/life/sleeping.htm


February 22, 2010 at 6:00 pm 3 comments


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